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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >The vacuolating toxin from Helicobacter pylori forms hexameric pores in lipid bilayers at low pH
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The vacuolating toxin from Helicobacter pylori forms hexameric pores in lipid bilayers at low pH

机译：来自幽门螺杆菌的空泡毒素在低pH下在脂质双层中形成六聚体孔

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摘要

Pathogenic strains of Helicobacter Pylori secrete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracelIular compartments enriched in markers for late endosomes and lysosomes. Themolecular mechanisms by which VaCA causes this vacuolationremain largely unknown. At neutral pH, VacA is predominantIy a water-soluble dodecamer formed by two apposinghexamers. In this report, we show by using atomic forcemicroscopy that below pH Proximately equals 5, VacA associates with anioniclipid bilayers to form hexameric membrane-associated com-plexes. We propose that water-soluble dodecameric Vacaproteins disassemble at low pH and reassemble into membrane-spanning hexamers. The surface contour of the membrane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface incontact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measurements indicate that, under the conditions determined byatomic force microscopy for membrane association, VacA forms pores across planar lipid bilayers. This low pH-triggered pore formation is likely a critical step in Vaca activity.
机译：幽门螺杆菌的致病性菌株分泌一种细胞毒素VacA，在弱碱的存在下，会引起酸性胞内区室的渗透性肿胀，富含晚期内体和溶酶体的标志物。 VaCA导致这种空泡化的分子机制仍然是未知的。在中性pH值下，VacA主要是由两种对位六聚体形成的水溶性十二聚体。在本报告中，我们通过原子力显微镜显示，低于pH值等于5时，VacA与阴离子脂质双层结合形成六聚体膜相关复合物。我们建议水溶性的十二聚体Vacaproteins在低pH值下会分解并重新组装成跨膜六聚体。与膜结合的六聚体的表面轮廓与可溶性十二聚醚的外表面极为相似，表明质子化之前，与膜接触的VacA表面被掩埋在十二聚体内。另外，电生理学测量表明，在通过原子力显微镜确定的膜缔合条件下，VacA在平面脂质双层上形成孔。低pH触发的孔形成可能是Vaca活性的关键步骤。

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